Cationic modified montmorillonite, its preparation and application method in defluorination

Abstract

The application discloses cation modified montmorillonite and a preparation method and application method thereof in defluorination, and belongs to the technical field of modified montmorillonite. The cation modified montmorillonite is hexadecyl trimethyl ammonium bromide and / or octadecyl trimethyl ammonium bromide modified montmorillonite; the application method comprises the following steps: adding the cation modified montmorillonite into a solution of perfluoro and polyfluoro alkyl substances (PFAS), adjusting the pH of the mixed solution to 11-13, and then carrying out hydrothermal reaction at 100-220 DEG C. The cation modified montmorillonite can mineralize PFAS efficiently under mild reaction conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of modified montmorillonite, in particular to a cationic modified montmorillonite and a preparation method and application method thereof in defluorination. BACKGROUND

[0002] Per- and polyfluoroalkyl substances (PFAS) are ubiquitous in the environment, wildlife, and humans, causing significant global concern. Due to the high bond energy of C-F bonds, the destruction of PFAS is extremely challenging, and the complete mineralization of PFAS into inorganic fluorides is also difficult to achieve.

[0003] Montmorillonite is one of the main component minerals of bentonite, which is a 2:1 type layered clay mineral. According to the type of exchangeable cations, it can be divided into four types: sodium-based, calcium-based, magnesium-based, and aluminum (hydrogen) based. Among them, sodium montmorillonite is the most common. + Montmorillonite has significant hydrophilic characteristics due to the negative charge on its surface, and its adsorption effect on weakly polar and non-polar organic pollutants is not good, which limits its application range to some extent. In the prior art, in order to improve its adsorption capacity, the interlayer exchangeable cations or structural water of montmorillonite are often replaced by organic functional groups or organic matter to improve its adsorption performance on hydrophobic organic matter.

[0004] However, the modified montmorillonite obtained by the existing modification method can only perform certain adsorption defluorination on perfluorinated compounds, and cannot truly realize the mineralization of perfluorinated compounds, i.e., converting them from organic fluorides to inorganic fluoride ions. SUMMARY

[0005] In view of the defects of the prior art, the purpose of the present application is to provide a new type of cationic modified montmorillonite and a preparation method and application method thereof in defluorination. The application method can efficiently mineralize perfluoroalkyl substances and polyfluoroalkyl substances (PFAS) under mild reaction conditions by using montmorillonite modified by cationic surfactants such as hexadecyl trimethyl ammonium bromide and / or octadecyl trimethyl ammonium bromide.

[0006] The technical solution of the present application is as follows:

[0007] A preparation method of a cationic modified montmorillonite, comprising: dissolving sodium montmorillonite in hot water, then adding a cationic surfactant for mixing and impregnation, washing and drying the impregnated sodium montmorillonite to obtain the cationic modified montmorillonite; wherein the cationic surfactant is selected from hexadecyl trimethyl ammonium bromide and / or octadecyl trimethyl ammonium bromide.

[0008] According to some preferred embodiments of the present application, the temperature of the hot water is 60-80℃.

[0009] According to some preferred embodiments of the present application, the time for the mixed impregnation is 1-3h.

[0010] According to some preferred embodiments of the present application, the temperature for the drying is 50-70℃.

[0011] According to some preferred embodiments of the present application, the mass ratio of the sodium-montmorillonite to the cationic surfactant is 10:3-10:8.

[0012] The present application further provides a cation-modified montmorillonite prepared according to the above preparation method.

[0013] Compared with sodium-montmorillonite, the interlayer spacing of the cation-modified montmorillonite is increased, such as from 1.27nm to 3.47nm, and the introduction of the cationic surfactant leads to charge reversal, i.e. the surface of the montmorillonite is converted to be positively charged.

[0014] The present application further provides an application method of the obtained cation-modified montmorillonite in defluorination, which comprises applying the cation-modified montmorillonite in the mineralization of perfluoroalkyl and / or polyfluoroalkyl substances, i.e. PFAS.

[0015] According to some preferred embodiments of the present application, the application method comprises:

[0016] adding the cation-modified montmorillonite into a solution of PFAS, and mixing to obtain a mixed solution;

[0017] adjusting the pH of the mixed solution to 11-13 to obtain a mixed system;

[0018] subjecting the mixed system to a hydrothermal reaction at 100-220℃ for 2-8h to obtain a defluorination solution.

[0019] The above application method of the present application can enrich PFAS to the surface and interlayer of the cation-modified montmorillonite, and then completely mineralize the PFAS by a hydrothermal reaction, and the defluorination rate is significantly improved compared with direct adsorption of the cation-modified montmorillonite or direct hydrothermal degradation of PFAS, and the inventors have unexpectedly found that in the above application method of the present application, PFAS not only undergoes adsorption and hydrothermal degradation, but also reacts with the cation-modified montmorillonite, so that the fluorocarbon bond in PFAS is broken, and the organic PFAS can be fully converted into inorganic fluoride ions.

[0020] Meanwhile, the inventors have unexpectedly found that the pH value of the mixed system without pH adjustment, i.e. the background pH value, is about 8.4, when the pH is adjusted to be greater than 8.4-10, the defluorination rate will decrease to a certain extent, and when the pH is further adjusted to be higher than 11, the defluorination rate will be significantly improved.

[0021] According to some preferred embodiments of the present application, the closed mixing time is 3-5h.

[0022] According to some preferred embodiments of the present application, the application method comprises adjusting the pH of the mixed solution to 12.5.

[0023] The inventors have surprisingly found that this pH value can achieve a better defluorination rate.

[0024] According to some preferred embodiments of the present application, the application method comprises hydrothermal reaction of the mixed system at 200℃ for 6h.

[0025] The inventors have surprisingly found that this hydrothermal reaction temperature and time can achieve a better defluorination rate and lower energy consumption.

[0026] According to some preferred embodiments of the present application, in the cation-modified montmorillonite, the molar ratio of the cationic surfactant to the cation exchange capacity of sodium-montmorillonite is 1.55.

[0027] The inventors have surprisingly found that this raw material ratio can achieve a better defluorination rate.

[0028] According to some preferred embodiments of the present application, the PFAS comprises long-chain PFAS such as perfluorooctanoic acid and short-chain PFAS such as trifluoroacetic acid.

[0029] The beneficial effects of the present application include:

[0030] The cation-modified montmorillonite obtained by the present application has good defluorination effect;

[0031] Compared with the traditional high-temperature hydrothermal treatment method, the defluorination application method of the present application has mild reaction conditions, low energy consumption, is friendly to the environment, and has higher defluorination effect and faster defluorination speed; compared with the traditional adsorption method, the defluorination application method of the present application does not require high-cost post-processing, and has higher defluorination rate and faster defluorination speed;

[0032] In the defluorination application method of the present application, PFAS can be adsorbed and enriched and then chemically reacted with the cation-modified montmorillonite, causing the breaking of the fluorocarbon bond and realizing the complete mineralization of PFAS.

[0033] Compared with the traditional defluorination method in liquid-liquid homogeneous phase, the defluorination application method of the present application can realize the synergistic effect of mineral-alkali-PFAS heterogeneous system, which is suitable for the complex scenario that PFAS is commonly adsorbed on soil / sediment (solid phase) in the real environment, and has stronger practical applicability.

[0034] The defluorination application method of the present application has good defluorination effect on long-chain PFAS (such as perfluorooctanoic acid) and short-chain PFAS (such as trifluoroacetic acid). BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The X-ray diffraction comparison chart of Na-Mt, Na-Mt@CTAB, Na-Mt@CTAB after adsorbing PFOA, and the sample after adsorption and hydrothermal reaction in Example 1.

[0036] Figure 2 The defluorination effect comparison chart of different defluorination treatments on PFOA in Example 1.

[0037] Figure 3 The defluorination effect comparison chart of different defluorination treatments on PFOA in Example 2.

[0038] Figure 4 The defluorination effect chart of defluorination treatment on trifluoroacetic acid in Example 3.

[0039] Figure 5 The defluorination effect comparison chart of different defluorination treatments on PFOA in Example 4.

[0040] Figure 6 The defluorination effect comparison chart of different defluorination treatments on PFOA in Example 5.

[0041] Figure 7 The defluorination effect comparison chart of different Na-Mt@CTAB on PFOA in Example 6.

[0042] Figure 8 The defluorination effect comparison chart of different defluorination treatments on PFOA in Comparative Examples 1-3.

[0043] Figure 9 The defluorination effect comparison chart of different defluorination treatments on PFOA in Comparative Example 4.

[0044] Figure 10 The defluorination effect comparison chart of different defluorination treatments on PFOA in Comparative Example 5. DETAILED DESCRIPTION

[0045] The technical solutions in the present application will be further described below in combination with the embodiments and drawings of the present application. The embodiments described below are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should fall within the scope of protection of the present application.

[0046] The fluoride ion concentration in the following examples is measured by a fluoride ion electrode (Orion Dual Star pH / ISE dual-channel benchtop meter), and the defluorination rate is obtained according to the following calculation formula:

[0047] Defluorination rate = (C F -V 液 ) / C0V0P F ×100%

[0048] Wherein, C F represents the measured concentration of fluoride ions in the solution (mg / L), V 液 is the corresponding solution volume, C0is the concentration of the initial perfluorooctanoic acid solution (mg / L), V0is the volume of the initial perfluorooctanoic acid solution (mL), P F is the proportion of the amount of fluorine atoms in the molecular weight of perfluorooctanoic acid.

[0049] Example 1

[0050] The hexadecyl trimethyl ammonium bromide (CTAB) modified montmorillonite Na-Mt@CTAB is prepared by the following method:

[0051] Take 10g sodium-montmorillonite (Na-Mt) and dissolve it in 100ml 70℃ water, stir at a speed of 650r / min for 1h, then add 6g hexadecyl trimethyl ammonium bromide (CTAB) and continue to stir at a speed of 650r / min for 2h, wash with 1L ultrapure water, then centrifuge at a speed of 8000rpm for 5min, and dry the obtained product in a 60℃ oven for 24h to obtain a Na-Mt@CTAB solid sample (1.55CEC-Mt@CTAB).

[0052] The obtained Na-Mt@CTAB solid sample is subjected to defluorination application, including the following steps:

[0053] (1) Add 20mL perfluorooctanoic acid (PFOA) solution with a concentration of 20mg / L to a 50mL reaction kettle, then add 1g Na-Mt@CTAB, stir for 4h, then adjust the pH to 12.5 by sodium hydroxide (NaOH) to obtain a mixed system;

[0054] (2) The mixed system is subjected to hydrothermal reaction at 220℃, 200℃, 180℃, 160℃ and 120℃ respectively for 6h to obtain a defluorination liquid.

[0055] Furthermore, the fluoride ion content in the defluorination solution was determined by the following method: ultrapure water was added to the defluorination solution and ultrasonic treatment was performed at 100 Hz for 15 min, followed by centrifugation at 10000 rpm for 5 min. The supernatant obtained by centrifugation was taken out and filtered through a 0.22 μm polyethersulfone filter membrane to obtain the analytical solution. The analytical solution was diluted to 20 ml with ultrapure water and the fluoride ion concentration was determined by a fluoride ion electrode.

[0056] X-ray diffraction characterization was performed on Na-Mt@CTAB (Mt@CTAB shown in the figure) prepared in Example 1, the sample after direct adsorption of perfluorooctanoic acid (adsorption method: Na-Mt@CTAB and perfluorooctanoic acid solution were stirred at 650 r / min for 4 h at room temperature) (A-Mt@CTAB), and the samples after adsorbing perfluorooctanoic acid through the above defluorination application and undergoing hydrothermal reaction at 200℃ (H-Mt@CTAB and H-12.5-Mt@CTAB, both of which were samples after hydrothermal reaction at 200℃). The results are shown in the appendix. Figure 1 As shown, unmodified sodium-montmorillonite (Na-Mt) is used as a reference.

[0057] from Figure 1 It can be seen that Na-Mt has characteristic diffraction peaks belonging to sodium montmorillonite with the (001) crystal plane; after CTAB modification, the peak of the (001) crystal plane shifts to the left, and the interlayer spacing of the (001) crystal plane increases, indicating that CATB... + Ions enter the Mt interlayer; while the (001) crystal plane of the sample after direct adsorption of perfluorooctanoic acid solution continues to increase, indicating that perfluorooctanoic acid has entered the Na-Mt@CTAB interlayer; and after adsorption and hydrothermal reaction, the interlayer spacing of the (001) crystal plane decreases, indicating that perfluorooctanoic acid has been degraded.

[0058] The concentrations of fluoride ions in the analytical solution at different hydrothermal reaction temperatures measured in Example 1 were statistically analyzed, and the results are shown in the appendix. Figure 2 As shown, the defluorination rate corresponding to a hydrothermal reaction temperature of 120℃ is 18.03%, indicating that there are relatively few carbon-fluorine bond breaks in PFOA. The defluorination rate increases to 39.34% at 160℃, 72.64% at 180℃, and 81.58% at 200℃. Further increasing the temperature to 220℃, the defluorination rate is 84.47%. It can be seen that when the temperature is increased from 200℃ to 220℃, the defluorination rate only increases by less than 3 percentage points. The increase in defluorination rate due to the increase in temperature is not significant compared with the additional energy consumption / cost. Considering the balance between defluorination efficiency and energy consumption, 200℃ is the better hydrothermal reaction temperature.

[0059] Example 2

[0060] Octadecyltrimethylammonium bromide (STAB) modified montmorillonite Na-Mt@STAB was prepared by the following method:

[0061] 10 g of sodium-montmorillonite (Na-Mt) was dissolved in 100 ml of water at 70°C, stirred at a speed of 650 r / min for 1 h, then 6 g of octadecyltrimethylammonium bromide (STAB) was added and continued to be stirred at a speed of 650 r / min for 2 h, washed with 1 L of ultrapure water, then centrifuged at a speed of 8000 rpm for 5 min, and the obtained product was dried in an oven at 60°C for 24 h to obtain a Na-Mt@STAB solid sample.

[0062] The obtained Na-Mt@STAB solid sample was subjected to defluorination application, including the following steps:

[0063] (1) 20 mL of perfluorooctanoic acid (PFOA) solution with a concentration of 20 mg / L was added to a 50 mL reaction kettle, then 1 g of Na-Mt@STAB was added, and stirred for 4 h, then the pH was adjusted to 12.5 by sodium hydroxide (NaOH) to obtain a mixed system;

[0064] (4) The mixed system was subjected to hydrothermal reaction at 220°C, 200°C, 180°C, 160°C and 120°C respectively for 6 h to obtain a defluorination liquid.

[0065] Further, the analysis solution was prepared by the same method as in Example 1 and the concentration of fluoride ions was determined, and the statistical results are shown in Table 1. Figure 3 As can be seen, the defluorination rate corresponding to the hydrothermal reaction temperature of 120°C is 17.22%, indicating that there is less breaking of carbon-fluorine bonds in PFOA, the defluorination rate increases to 45.51% at 160°C, to 51.12% at 180°C, to 79.16% at 200°C, and further increasing the temperature to 220°C, the defluorination rate is 81.75%, indicating that octadecyltrimethylammonium bromide (STAB) modified Na-Mt also has good defluorination effect.

[0066] Example 3

[0067] Na-Mt@CTAB solid sample was subjected to defluorination application in the manner of Example 1, the only difference being that the solution for defluorination was a short-chain PFAS trifluoroacetic acid solution, i.e. 20 mL of trifluoroacetic acid (TFA) solution with a concentration of 20 mg / L was added to a 50 mL reaction kettle, and the mixed system was subjected to hydrothermal reaction at 200°C for 6 h to obtain a defluorination liquid.

[0068] The analysis solution was prepared by the same method as in Example 1 and the concentration of fluoride ions was determined, and the statistical results are shown in Table 1. Figure 4 ​

[0069] Example 4

[0070] The Na-Mt@CTAB solid sample was defluorinated in the same manner as in Example 1, except that the pH was adjusted to 12, 12.5 and 13 respectively, and the mixed system was hydrothermally reacted at 200°C for 6h to obtain the defluorinated liquid.

[0071] The analysis liquid was prepared in the same manner as in Example 1 and the concentration of fluoride ion was determined, and the statistical results are shown in Table 2. Figure 5

[0072] It can be seen that with the increase of pH, the defluorination rate first increases and then decreases, specifically, when the pH is 12, the defluorination rate is 47.92%, when the pH is 12.5, the defluorination rate is 81.58%, and when the pH is 13, the defluorination rate is 55.07%, therefore, the pH=12.5 is the preferred pH value.

[0073] Example 5

[0074] The Na-Mt@CTAB solid sample was defluorinated in the same manner as in Example 1, except that the mixed system was hydrothermally reacted at 200°C for 4h, 6h and 8h respectively to obtain the defluorinated liquid.

[0075] The analysis liquid was prepared in the same manner as in Example 1 and the concentration of fluoride ion was determined, and the statistical results are shown in Table 3. Figure 6

[0076] It can be seen that with the increase of hydrothermal reaction time, the defluorination rate first increases and then decreases, specifically, when the hydrothermal reaction time is 4h, the defluorination rate is 67.07%, when the hydrothermal reaction time is 6h, the defluorination rate is 81.58%, and when the hydrothermal reaction time is 8h, the defluorination rate is 77.97%, therefore, the preferred hydrothermal reaction time is 6h.

[0077] Example 6

[0078] The Na-Mt@CTAB solid sample was prepared in the same manner as in Example 1, except that the amount of added cetyltrimethylammonium bromide (CTAB) was 6 and 7.72g respectively, and two kinds of Na-Mt@CTAB solid samples were obtained with the molar ratio of CTAB to CEC (Cation Exchange Capacity, 106mmol / 100g) being 1.55 and 2 respectively.

[0079] The two kinds of obtained Na-Mt@CTAB solid samples were defluorinated in the same manner as in Example 1, except that the mixed system was hydrothermally reacted at 200°C for 6h to obtain the defluorinated liquid.

[0080] The analysis liquid was prepared in the same manner as in Example 1 and the concentration of fluoride ion was determined, and the statistical results are shown in Table 4.​​Figure 7 As shown.

[0081] It can be seen that the defluorination rate of 1.55 CEC-Mt@CTAB is 81.58%, and the defluorination rate of 2 CEC-Mt@CTAB is 70.72%, which indicates that the defluorination rate of 1.55 CEC-Mt@CTAB is better than that of 2 CEC-Mt@CTAB. The defluorination rate of 2 CEC-Mt@CTAB is 70.72%, which may be due to the fact that 1.55 CEC-Mt@CTAB is closer to monolayer coverage, and the quaternary ammonium salt molecules are uniformly distributed on the mineral surface in a flat manner, forming a dense hydrophobic layer, which can improve the adsorption of PFAS pollutants, and further increasing the amount of CTAB to 2 CEC may form a double layer or micellar structure, resulting in site shielding, and the outer layer CTAB covers the inner layer active site, reducing the contact opportunity with PFAS.

[0082] Comparative Example 1

[0083] The unmodified sodium-montmorillonite was subjected to defluorination as follows:

[0084] Into a 50 mL reaction kettle, 20 mL of perfluorooctanoic acid (PFOA) solution with a concentration of 20 mg / L was added, followed by the addition of 1 g of unmodified Na-Mt. After stirring for 4 h, a defluorination liquid was obtained.

[0085] Comparative Example 2

[0086] The Na-Mt@CTAB adsorption defluorination treatment was carried out by the following process:

[0087] Into a 50 mL reaction kettle, 20 mL of perfluorooctanoic acid (PFOA) solution with a concentration of 20 mg / L was added, followed by the addition of 1 g of Na-Mt@CTAB solid sample prepared in Example 1. After stirring for 4 h, a defluorination liquid was obtained.

[0088] Comparative Example 3

[0089] The unmodified sodium-montmorillonite was subjected to defluorination as follows:

[0090] Into a 50 mL reaction kettle, 20 mL of perfluorooctanoic acid (PFOA) solution with a concentration of 20 mg / L was added, followed by the addition of 1 g of unmodified Na-Mt. After stirring for 4 h, a mixed system was obtained.

[0091] The mixed system was subjected to hydrothermal reaction at 200°C for 6 h to obtain a defluorination liquid.

[0092] Comparative Example 4

[0093] The perfluorooctanoic acid (PFOA) hydrothermal defluorination treatment was carried out by the following process:

[0094] Add 20 mL of a 20 mg / L perfluorooctanoic acid (PFOA) solution to a 50 mL reactor. Perform hydrothermal reactions at 200 °C for 6 h, with and without pH adjustment, and with pH set to 12.5, respectively, to obtain a defluorinated solution.

[0095] Comparative Example 5

[0096] CATB hydrothermal defluorination is performed through the following process:

[0097] Add 20 mL of 20 mg / L perfluorooctanoic acid (PFOA) solution to a 50 mL reactor, then add 1 g of CATB, and stir in a sealed container for 4 h to obtain a mixed system.

[0098] The mixture was subjected to a hydrothermal reaction at 200°C for 6 hours, with and without pH adjustment of the mixture, and with pH adjusted to 12.5, respectively, to obtain a defluorination solution.

[0099] The defluorination solutions of Comparative Examples 1-5 were prepared into analytical solutions and their fluoride ion concentrations were determined using the same method as in Example 1. The statistical results for Comparative Examples 1-3 are shown in the attached figure. Figure 8 As shown (ND indicates a defluorination rate of 0), the statistical results of Comparative Example 4 are attached. Figure 9 As shown in the attached figure, the statistical results for Comparative Example 5 are as follows. Figure 10 As shown.

[0100] pass Figure 8 It can be seen that the defluorination rate of pure sodium-montmorillonite (Na-Mt) adsorbing PFOA solution (Comparative Example 1) and the direct adsorption of PFOA solution by modified Na-Mt@CTAB (Comparative Example 2) is 0. The defluorination rate of pure sodium-montmorillonite (Na-Mt) adsorbing PFOA solution and undergoing hydrothermal reaction at 200℃ for 6 hours (Comparative Example 3) is only 1.48%. This indicates that the adsorption of pure Na-Mt and modified Na-Mt@CTAB, as well as the adsorption of Na-Mt followed by hydrothermal treatment, cannot significantly achieve the cleavage of carbon-fluorine bonds in PFOA.

[0101] pass Figure 9 It can be seen that when PFOA solution is directly hydrothermally degraded without pH adjustment, the defluorination rate is 0. When the pH is adjusted to 12.5, the defluorination rate is only 3.17%, indicating that the defluorination rate of PFOA by direct hydrothermal degradation is very low regardless of whether the pH value is adjusted.

[0102] pass Figure 10 It can be seen that when PFOA is adsorbed and degraded using the surfactant CTAB without pH adjustment, the defluorination rate is 3.45%. When the pH is adjusted to 12.5, the defluorination rate is only 16.58%, indicating that the surfactant CTAB cannot achieve efficient defluorination regardless of whether it is under strong alkaline conditions.

[0103] It should be noted that the above only describes the preferred embodiments of the present application, which should not limit the protection scope of the technical solutions of the present application. Any modification made by those skilled in the art to the technical solutions described in the foregoing embodiments, equivalent replacement of technical features, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for applying cationic modified montmorillonite in defluorination, characterized in that, The cationic modified montmorillonite is obtained by: dissolving sodium-montmorillonite in hot water at 60-80℃, then adding a cationic surfactant and mixing and impregnating for 1-3 hours, washing and drying the impregnated sodium-montmorillonite to obtain the cationic modified montmorillonite; wherein the cationic surfactant is selected from hexadecyltrimethylammonium bromide and / or octadecyltrimethylammonium bromide; the mass ratio of sodium-montmorillonite to the cationic surfactant is 10:3-10:8; The application method includes: The cationic modified montmorillonite was added to a solution of perfluoroalkyl and / or polyfluoroalkyl substances, i.e., PFAS, and mixed in a closed system to obtain a mixture. The pH of the mixture was adjusted to 11-13 to obtain the mixed system; The mixture was subjected to a hydrothermal reaction at 100-220℃ for 2-8 hours to obtain a defluorinated liquid.

2. The application method according to claim 1, characterized in that, The drying temperature is 50-70℃.

3. The application method according to claim 1, characterized in that, in, The sealed mixing time is 3-5 hours.

4. The application method according to claim 1, characterized in that, It includes: Adjust the pH of the mixture to 12.5; And / or, subject the mixture to a hydrothermal reaction at 200°C for 6 hours.

5. The application method according to claim 1, characterized in that, In the cationic modified montmorillonite, the molar ratio of the cationic surfactant to the cation exchange capacity of sodium-montmorillonite is 1.

55.

6. The application method according to claim 1, characterized in that, The PFAS includes long-chain PFAS and short-chain PFAS.

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